If I were to implement this (and I have thought about it from time to time), I would first create an incoming mail rule for the (ultimate) recipient account to direct these messages to a PIPE for processing by a Perl script. Then, I would hold them up for a configurable amount of time 30-60 seconds, and if I had more than one message in the bin, compare the headers and content and apply a weight to one list over another, ultimately discarding the "excess ones" and (re) submitting the weighted one to the user's mailbox.

I just have never worked out the mechanics of the process. For me, while REXX is a native scripting language (on OS/2), I would still likely opt for Perl simply because its string manipulation is so good.

Mailing lists are processed independently.
Postings through different lists replace Message-Id with different
values, the original Message-Id is not necessarily kept.
The postings are delivered independently.

How do we know the next posting to be delivered into a mailbox of a
subscriber is a duplicate of another? At the moment the message is to be
stored we need to either search the destination mailbox for a duplicate
Message-Id, or keep a track of recently delivered ones. The former is
too expensive, the accuracy of the latter may be affected by many
factors: flow rate for the given account, delays in distributions, etc.

On 2016-08-12 17:46 , Bob D wrote:
> Amen to this. I would like to see this as well.
>
> Bob
>
>
> On Fri, 12 Aug 2016 10:44:12 -0400
> Mark J Strawcutter <mjstraw@iup.edu> wrote:
>> I've asked for this for over 10 years
>>
>> Mark
>>
>> On 8/12/2016 2:41 AM, Paul_Dudley wrote:
>>> If a person is a member of multiple distribution lists, and someone else
>>> sends an email to two or more of these distribution lists, is there a
>>> way to filter the message so that the recipient only receives the email
>>> once?
>>>
>>>
>>> For example if I am a member of distribution lists a@domain.com
>>> <mailto:a@domain.com>, b@domain.com <mailto:b@domain.com> and
>>> c@domain.com <mailto:c@domain.com>, and someone sends an email to all
>>> three distribution lists, is there a way to ensure I only receive the
>>> email once instead of three times?
>>>
>>>
>>> Thanks & Regards
>>>
>>> Paul Dudley
>>>
>>> IT Operations
>>>
>>> *ANL Container Line*
>>>
>>> *pdudley@anl.com.au*
>>>
>>>
>>> *_ANL DISCLAIMER_*
>>>
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>>> do not copy, use or make reference to it for any purpose, or disclose
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--
Best regards,
Dmitry Akindinov.
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